PURPOSE: This randomized phase II/III trial is studying the side effects of giving clofarabine compared with giving high-dose cytarabine, pegaspargase, and combination chemotherapy followed by daunorubicin hydrochloride or doxorubicin hydrochloride and to see how well it works in treating young patients with T-cell acute lymphoblastic leukemia or precursor B-cell acute lymphoblastic leukemia.